For astronauts engaged in extravehicular activity in the space environment, it is necessary to provide protection against a variety of environmental hazards. Included among such hazards is the corrosive effect of the various chemicals employed in spacecraft operations. An astronaut's contact with or close proximity to spacecraft chemical propellants as might occur during extravehicular refueling or propellant handling operations can result in structural degradation of the astronaut's space suit, helmet and visor assembly to a degree which greatly increases the danger from impacts with micrometeoroids, dust particles or space debris. In addition, the visor may become pitted and eroded to a degree which severely reduces the transparency of the visor and impairs the vision of the astronaut. With the prospect of long-term space missions associated with the deployment of space stations and lunar base or planetary surface operations, the hazards presented by such structural limitations of space suit helmets and visors will be greatly increased.
The helmets and visor assemblies which have been incorporated in space suits used in previous space programs have not incorporated any active or passive protective techniques for providing spacecraft propellant and chemical hazards protection. Although polycarbonate, which is currently used in space helmet construction, possesses some chemical resistant properties, it is structurally degradable on exposure to a variety of spacecraft propellants and other chemicals involved in extravehicular refueling and handling operations. In the prior art of protective garments with chemical resistant properties, U.S. Pat. No. 4,226,301 discloses a protective hood for protecting flight crew members from chemical-biological agents. The hood includes a helmet covering with a transparent lens of polycarbonate material. U.S. Pat. Nos. 4,199,648 and 4,082,891 disclose chemically resistant coatings for polycarbonate articles which coatings comprise the photoreaction product of a polythiol and a polyene.
U.S. Pat. No. 3,437,631 discloses a helmet fabricated from a mixture of polycarbonate resin and polyolefin, and
U.S. Pat. Nos. 3,933,734 and 4,201,832 each disclose a polycarbonate composition which includes sulfuric acid or sulfonates and provides improved chemical resistance. While these prior art devices are suitable for many activities, they are unsuited for use in space helmets and visors.